/usr/lib/x86_64-linux-gnu/libpython3.6dm.a is in libpython3.6-dbg 3.6.5-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/../python3.6/config-3.6dm-x86_64-linux-gnu/libpython3.6dm.a